Isomerization of paraffinic hydrocarbons with trifluoromethanesulfonic acid

ABSTRACT

Paraffinic hydrocarbons are converted to other hydrocarbons by contacting with a catalyst comprising trifluoromethanesulfonic acid. In another embodiment, normal paraffins are isomerized with high selectivity to skeletal isomers containing the same number of carbon atoms by contacting same with a catalyst comprising trifluoromethanesulfonic acid and a Group Vb metal fluoride.

United States Patent [191 Norell [111 3,855,346 8 [451 Dec. 17, 1974ISOMERIZATION OF PARAFFI NIC HYDROCARBONS WITH TRIFLUOROMETHANESULFONICACID [75] Inventor: John R. N0rell, Bart1esville,' Okla.

[73] Assignee: Phillips Petroleum Company,

- Bartlesville, Okla.

[22] Filed-: Jan. 28, 1972 [21] App]. N0.: 221,777

[52] US. Cl. 260/683.68

[51] Int. Cl.; C070 5/30 [58] Field of Search..... 260/683,68, 683.47,683.58, 260/668 A, 683.65, 666 P; 252/439, 441

[56] References Cited UNITED STATES PATENTS 3.594.445 7/1971 Parker260/68368 3,636,129 1/1972 Parker et a1. 260/683.58 3,678,120 7/1972Bloch 260/683.65 3,766,286 10/1973 Olah 260/683.68

Primary Examiner-Delbert E. Gantz Assistant Examiner-G. J. Crasanakis 57ABSTRACT Paraffinic hydrocarbons are converted to other hydrocarbons bycontacting with a catalyst comprising trifluoromethanesulfonic acid.- Inanother embodi- Vb metal fluoride.

3 Claims, N0 Drawings ISOMERIZATION OF PARAFFINIC I-IYDROCARBONS WITHTRIFLUOROMETHANESULFONIC AClID a catalyst comprisingtrifluoromethanesulfonic acidand a Group Vb metal fluoride. Inaccordance with a further aspect, normal paraffims are isomerized withhigh selectivity to skeletal isomers containing the same number ofcarbon atoms by contacting the parafflns with a catalyst comprisingtrifluoromethanesulfonic acid and a Group Vb metal fluoride.

It is well known that the more highly branched, isomers of theparaffinic hydrocarbons occurring in petroleum gasoline fractions aremore valuable than the corresponding slightly branched or straight chainhydrocarbons because of their higher octane ratings. The demand formotor fuels of greater octane number has-increased markedly as theautomotive industry has provided gasoline engines with increasinglyhigher compression ratios to attain greater efficiency. One of theeconomically important ways in which the increased demands for highoctane fuels can be-met is through the isomerization of the lightnaphtha components of such fuels.

It may be generally stated that the isoparaffinic and branchedchain'paraffin hydrocarbons are of greater commercial value to thepetroleum industry than the corresponding straight chain hydrocarbons.Thus, for example, 2.2-.dimethylbutane has a higher octane rat: ing thanthe isomeric normal hexane. Isobutane is more valuable than normalbutane since the former can be used as a basis for the preparation of8-carbon-atom, branched chainhydrocarbons by alkylation with butylene.

The isomerization of normal paraffinhydrocarbons I into thecorresponding branched chain homologsis well known. For effecting theisomerization, it is ,customary to employ certain metal halides,particularly aluminum chloride or aluminum bromide, in conjunction withcertain promoters such as hydrogen chloride, hydrogen bromide, or boronfluoride. Recently, strong acid systems such as solutions offluorosulfonic acid and antimony pentafluoride have also beendisclosed'as useful isomerization catalysts. An important problemarising with the use of these highly active catalysts is that theypromote side reactions such as cracking and disproportionation. Theseside reactions are particularly evident at high conversion conditionsand lead to the formation of substantial amounts of undesirable lightand/or heavy side products.

Accordingly,'an object of this invention is to provide an improvedhydrocarbon conversion process.

Another object of this invention is to provide an isomerization processwhereby high selectivity to skeletal isomers is achieved.

Another object of this invention is to provide an improved isomerizationprocess for the conversion of paraffmic hydrocarbons.

' .2 hours, are .employed.

A further object of this invention is to provide an improved catalystfor hydrocarbon conversion and isomerization.

Other objects and aspects as well as the several advantages of theinvention will be apparent tothose skilled in the art upon furtherconsideration of the specification and the appended claims.

In accordance with the invention, a process for the conversion ofparaffinic hydrocarbons to other hydrocarbons is provided whichcomprises contacting the hydrocarbons with a catalyst comprisingtrifluoromethanesulfonic acid. It has been found thattrifluoromethanesulfonic acid alone effects the isomerization andcracking of paraffinic hydrocarbons such as normal hexane.

Further in accordance with the invention, it has been found thatnormalparaffins can be isom'erized with high selectivity to branchedisomers containing the 7 same number of carbon atoms by contacting thehydrocarbons with a catalyst comprising trifluoromethanesulfonic acidand a Group Vb metal fluoride.

In accordance with one specific embodiment, nhexane isomerizes topredominantly neohexane in the presence of a catalyst comprisingtrifluoromethanesulfonic acid and at least one of phosphoruspentafluoride, antimonypentafluoride.and arsenic pentafluoride.

Trifluoromethanesulfonic acid has various advantages not possessed byknown superacid catalyst systems including (1) it has a much higherboiling point, hence less is loston recycle in continuous operation; (2)it does not attack glass so sight gages, etc. made of glass can be used;and (3) it is the strongest protonic acid known and fective.

The catalyst composition of the presentinvention comprisestrifluoromethanesulfonic acid alone or trifluoromethanesulfonic acidwith a metal fluoride of aGroup Vb element. Specific examples of thesemetal paraffinic hydrocarbon stream, it is also contemplated.

that mixtures. of various paraffinic hydrocarbons can be employed. I

The reaction conditions for isomerization of the feed can be in therange of 0 to 100 C, usually 15 to C, and pressures sufficient tomaintain the hydrocarbon reactants and catalysts as liquid in thereaction zone,

-and the temperatures and pressures should be chosen accordingly. Thetime of contact is subject to wide variation, the length of residencetime dependent in part upon the temperature and catalyst concentrationemployed. In general, reaction times ranging from about 5 minutes to 48hours, preferably 15 minutes to about The mole ratio of paraffinichydrocarbon to Group Vb metal fluoride forming the catalyst of theinvention will generally be in the range 50:1 to 0.221, preferably 1:1to 20: l The mole ratio of trifluoromethanesulfonic acid to Group Vbmetal fluoride catalyst will generally hence smaller amounts of acid areefbe in the range 100:1 to 02:1, preferably 1:1 to 20:1. The mole ratioof trifluoromethanesulfonic acid to paraffinic hydrocarbon whentrifluoromethanesulfonic acid alone is used as the catalyst willgenerally be in the into a polyethylene separatory funnel. The upper hy-.drocarbon layer was drained under nitrogen into a Fischer-PorterAerosol compatibility bottle containing about five grams of potassiumcarbonate and cooled in range 0121 to 50:1, preferably 0.5:1 to 20:1. 5a dry ice-acetone bath. The bottle was quickly capped The process of theinvention is conducted as a batch with a heafl hg a Pressure g and aSlhcohe D" or a continuous operation. The apparatus employed m forwlthclrawmg Samples Phg analyses- Results can be ofa conventional natureand can comprise a sinare reported In terms of selechvmes based on theglc gle reactor equipped with sufficient stirring devices. analyses-Good agitation is important because the less dense par- EXAMPLE affinichydrocarbon layer is not miscible with the dense liqui ac phase. U recte reactants, ly Trifluoromethanesulfonic acid was used alone as theand other Pf 0f the macho can be separated catalyst to effect theisomerization and cracking of nfrom the desired product and from oneanother such as hexane i accordance i h h procedure Set f h by distllation and returned in whole or in part to the above. The isomerizationwas effected at a temperature isomerization zone. The resultant productcan be furof C for two hours. In both runs 25 ml (42.5 g, 0.28 therprocessed as by alkylation and the like or be emmole) oftrifluoromethanesulfonic acid and 17.2 g (0.2 ployed directly as a highoctane gasoline blending mole n-hexane were used. The results of thenormal agent. The reaction zone is preferably constructed of hexaneisomerization are given below in Table 1.

TABLE 1 Selectivity Hexane to Cracked Light Products Run Conv.,%Products (C C 'S,C 's) Heavies 2,2-DMB DlP+2-MP 3-MP materials which areresistant to corrosion by the catalyst. For example, the reactor can bea Monel lined re- 7 EXAMPLE I] actor. It is preferred that the reactionbe carried out o mal exane was isomerized to its branched isounderanhydrous conditions in an inert gas atmosphere. y Contacting with amixture of antimony P Trifluoromethanesulfonic acid fumes copiously uponfluoride (SbF and trifluoromethanesulfonic acid. In exposure to air andthe Group Vb metal halides are also n 3 and m1 gmole)trlflllOrOmethanehydrolyzed on exposure to atmospheric moisture.sulfonic acid and 17.2 g (0.2 mole) n-hexane were used. In runs 3 and 4,6.6 and 12.3 grams of antimony SPECIFIC EXAMPLES pentafluoride wereused, respectively. Paraffinic hydrocarbons were isomerized to isoparaf-The results of the normal hexane isomerization are fins with liquidphase catalyst systems of the invention 40 given below in Table II.

TABLE I1 lsomcrization of n-Hexanc with SbF /CF SO H at 25C/2 Hrs.

Hexanc Selectivity to Products Run Conv.,/r Cracked Products* Hca- VlCSutilizing a Monel reactor. The procedure for carrying out theisomerization in a Monel reactor is set forth below.

The process runs were carried out in a 300 ml Monel reactor. Thetrifluoromethanesulfonic acid was charged under nitrogen to the reactorand cooled therein to approximately 40C. In Examples 11, 111 and 1Vhereinbelow the Group Vb metal halide was then added to the coldtrifluoromethanesulfonic acid until the desired weight was obtained,followed by addition of the paraffin. The reactor was then capped andplaced in a thermostated Eberbach reciprocating shaker for any desirabletime at a specified tempera ture.

Workup involved cooling the Monelreactor in dry ice-acetone and thenrapidly pouring the cold mixture It can be seen from the above tabulateddata that antimony pentafluoride and trifluoromethanesulfonic acid inthe liquid phase effect hexane isomerization in 95 percent conversion tobranched C isomers with only three percent selectivity to cracked (C C15and C s) products. Neohexane formed in approximately the thermodynamicequilibrium quantity of 55 percent.

EXAMPLE 111 Normal hexane was isomerized to its branched isomers bycontacting with a mixture of trifluoromethanesulfonic acid andphosphorus pentafluoride at 25 C for 2 hours. In the run 12.6-grams (0.1mole) of phosphorus pentafluoride, 50 ml g, 0.56 mole)trifluoromethanesulfonic acid, and 17.2 g (0.2 mole) of n-hexane wereused. Results of the isomerization of n-hexane are given below in Table111.

TABLE 111 Selectivities* Mole Ratio n-C C l-C. n-C; 1-C5 2.2-DMB DIP &Run n-C JPB, "/1 Conv. 2-MP 3-MP Heavies *2.2 DMB represents 2.23-methylpentzmc.

It will be noted from the above table that trifluoromethanesulfonic acidin admixture with phosphorus pentafluoride effected hexane isomerizationin approximately 95 percent selectivity to branched C isomers-dimethylbutune. DIP represents diisopropyl (2.3-dimethylbutanc). 2-MPrepresents Z-methylpcntune. and 3-MP represents 2-MP dimethylbutane thanthe use of trifluoromethanesulfonic acid alone.

1 claim:

1. A process for the'isomerization of paraffinic hywith a n-hexaneconversion of 1.9 percent. drocarbons which comprises contacting a feedcornprising paraffinic hydrocarbons in a conversion zone at EXAMPLE IVisomerization conditions with a catalyst consisting of Hexane wasisomerized to branched products by conifluo methanesulfonic acid.

tacting with trifluoromethanesulfonic acid in admixture 2. A processaccording to claim 1 wherein the parafwith arsenic pe'ntafluoride at 25C for two hours. In the finic hydrocarbon is normal hexane. run 10.2 g(0.06 mole) of arsenic pentafluoride, 50 rnl 3. A process according toclaim 1 wherein said feed (85 g, 0.56 mole) trifluoromethanesulfonicacid, and comprises paraffinic hydrocarbons having from 4 to 7, 17.2 g(0.2 mole) of n-hexane were used. The results inclusive, carbon atomsper molecule and said contactof the isomerization are given below inTable IV. ing is effected at a temperature in the range of 0-100C TABLEIV Hexane I Selectivity to Li ht Products ,C s,C s) Heavies 2,2-DMBDlP-l-Z-MP 3-MP Run Conv.,% Cracked Products g and a pressuresufficientto maintain the reactants and catalyst in the liquid phase.

1. A PROCESS FOR THE ISOMERIZATION OF PARAFFINIC HYDROCARBONS WHICHCOMPRISES CONTACTING A FEED COMPRISING PARAFFINIC HYDROCARBONS IN ACONVERSION ZONE AT ISOMERIZATION CONDITIONS WITH A CATALYST CONSISTINGOF TRIFLUOROMETHANESULFONIC ACID.
 2. A process according to claim 1wherein the paraffinic hydrocarbon is normal hexane.
 3. A processaccording to claim 1 wherein said feed comprises paraffinic hydrocarbonshaving from 4 to 7, inclusive, carbon atoms per molecule and saidcontacting is effected at a temperature in the range of 0-100*C and apressure Sufficient to maintain the reactants and catalyst in the liquidphase.